附体与主体接合部的流场及不同连接形式对流场影响的试验研究

本文用氢气泡流场显示技术,实时观察了随时间变化的附体与主体相互干扰的马蹄涡流动的形成、发展和变化过程。采用的模型是用3:2椭圆作端部的NACA 0020翼型附体与一平板主体相连接,这是国际上最常用的模型。从实验的观察和分析出发,本文从物理意义上解释了接合部处产生低频振荡马蹄涡的机理,而且由此出发提出了控制低频振荡马蹄涡的一个简便方法,就是在附体与主体连接处以某一几何形状构造连接方式;对五种不同连接方式进行试验研究,发现弓形不对称连接方式为最佳,不但减弱了振荡同时也降低了涡强,从而证实了这种简便方法的实用性。

The Effect of Junction Form on Body-Appendage Junction Flows

The time-dependent features of an appendage-body junction flow formed around a foil with a 3:2 elliptical nose and a NASA 0020 tail are studied. The first phase results of the study are presented here. Hydrogen bubble flow visualizations have been used to study the time-dependent flows for a series height above the flate plate on which the foil stands. We observed that a junction vortex is formed at the corner between the foil and the flat plate. A strong suction is periodically developed between the vortex and the nose of the foil, which causes low frequency oscillation of the horse-shoe vortex.According to our observation and analysis, an efficient and simple method to reduce low frequency oscillation of the horse-shoe vortex is to give a suitable form at the foil-body corner. Five types of junction form are tested, with the result that the frequency of oscillation and the strength of the horse-shoe vortex may be effectively reduced by designing the suitable junction form.